Work vehicle

ABSTRACT

A work vehicle includes a vehicle body, a pair of left and right driving wheels that movably support the vehicle body, a pair of motors capable of rotatably driving the left and right driving wheels respectively, a pair of maneuvering levers pivotally supported to the vehicle body to be pivotable about a horizontal axis extending in a vehicle body transverse direction and capable of adjusting rotational speeds respectively of the left and right driving wheels and a pair of dynamic vibration absorbing portions supported to respective free end portions of the maneuvering levers and capable of suppressing vibrations of the maneuvering levers.

BACKGROUND OF THE INVENTION Field of the Invention

When a work vehicle is employed for a work such as a grass mowing workfor instance, the work often takes a prolonged period of time, so ridingcomfort and superiority/inferiority of operability of the work vehiclesignificantly affects the fatigue or discomfort of its riding person.For this reason, many of recent work vehicles, as shown in e.g. US2019/0016214A1, are equipped with a suspension or a vibration absorbingmechanism, thus alleviating the riding person's fatigue or discomfortthrough reduction of vibration.

Incidentally, with many work vehicles, a steering operation of wheels iseffected by a pair of right and left maneuvering levers. Vibrations dueto rotation of an engine, an electric motor, a mowing blade, of thevehicle body tends to be transmitted to such maneuvering levers. And,means for reducing vibrations, in a known arrangement, a sponge memberformed of e.g. ethylene propylene rubber, etc. is wound around the gripportion of the maneuvering lever.

SUMMARY OF THE INVENTION

However, if sympathetic vibration occurs in the maneuvering lever due tovibration of the vehicle body, this can lead to increase of vibration ofits free end portion. In addition, in the case of an arrangement inwhich the grip portion is provided at the free end portion of themaneuvering lever, even with presence of the sponge member at this gripportion, the vibration of the grip portion may not be suppressedfavorably. In view of this state of the art, an object of the presentinvention is to provide a work vehicle in which vibration of the gripportion is effectively suppressed.

A work vehicle according to the present invention comprises:

a vehicle body;

a pair of left and right driving wheels that movably support the vehiclebody;

a pair of motors (prime movers) capable of rotatably driving the leftand right driving wheels respectively;

a pair of maneuvering levers pivotally supported to the vehicle body tobe pivotable about a horizontal axis extending in a vehicle bodytransverse direction and capable of adjusting rotational speeds of theleft and right driving wheels respectively; and

a pair of dynamic vibration absorbing portions supported to respectivefree end portions of the maneuvering levers and capable of suppressingvibrations of the maneuvering levers.

With the present invention, dynamic vibration absorbing portions aresupported to each free end portion of the pair of left and rightmaneuvering levers respectively. In general, if the dynamic vibrationabsorbing portion has a natural frequency same as a resonance frequencyof the maneuvering lever, this dynamic vibration absorbing portion willvibrate in the reverse (opposite) phase relative to the vibration of themaneuvering lever, so that the vibration of the maneuvering lever can bereadily absorbed by this dynamic vibration absorbing portion. Therefore,even when sympathetic vibration occurs in the maneuvering lever due tovibration of the vehicle body, vibration of the free end portion of themaneuvering lever can be reduced effectively. For this reason, even whenthe riding person keeps gripping the maneuvering lever for a prolongedperiod of time, fatigue or discomfort for this driving person can bealleviated. Consequently, there is realized a work vehicle in whichvibration of the grip portion is effectively suppressed.

Preferably, in the above-described arrangement:

at the free end portion, there is provided a grip for a person ridingthe work vehicle to effect an operation of adjusting a rotational speedof the motor; and

the dynamic vibration absorbing portion is supported on more free endside than the grip.

With the above-described arrangement, since the dynamic vibrationabsorbing portion is supported on more free end side than the grip, thedynamic vibration absorbing portion can readily absorb the vibration ofthe grip. Namely, vibration damping is realized with a simplearrangement.

Preferably, in the above-described arrangement:

the dynamic vibration absorbing portion includes an elastic body and aweight; and

of the dynamic vibration absorbing portion, the elastic body issupported to the free end portion.

With the above-described arrangement, thanks to the arrangement of theelastic body being supported to the free end portion, this elastic bodyserves as a spring or a damper between the weight and the free endportion. Also, with the above arrangement, based on the weight of theweight and/or the material/shape of the elastic body chosen, it becomespossible to adjust the natural frequency of the dynamic vibrationabsorbing portion. Thus, through the simple arrangement of the weightand the elastic body, vibration of the free end portion of themaneuvering lever can be suppressed advantageously.

In the above-described arrangement, preferably:

the elastic body, at its center portion in the longitudinal direction,is formed like a hollow cylinder; and

the weight is engaged within the hollow center portion of the elasticbody.

With the above arrangement, as the weight is engaged within the hollowcenter portion of the elastic body, the weight is supported to theelastic body. Thus, the supporting arrangement for the weight and theelastic body can be made simple and the supporting arrangement of thedynamic vibration absorbing portion to the free end portion can be madesimple also.

In the above-described arrangement, preferably:

the free end portion is formed like a hollow pipe; and

the dynamic vibration absorbing portion is engaged within the hollowportion of the free end portion.

With the above arrangement, there is realized the simple arrangement ofthe dynamic vibration absorbing portion being engaged within the hollowportion of the free end portion.

In the above-described arrangement, preferably:

the dynamic vibration absorbing portion includes an elastic body and aweight;

the elastic body is formed like a hollow cylinder; and

the weight is engaged within a hollow center portion of the elasticbody.

With the above arrangement, there is realized the simple arrangement ofthe elastic body being engaged within the pipe-like hollow portion atthe free end portion and the weight being engaged within the hollowportion of the elastic body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side view of a riding type lawnmower,

FIG. 2 is a plan view of the riding type lawnmower,

FIG. 3 is an explanatory view illustrating a supporting arrangement of adynamic vibration absorbing portion to a free end portion and avibration model at the dynamic vibration absorbing portion,

FIG. 4 is an explanatory view illustrating an arrangement of the dynamicvibration absorbing portion being engaged within the free end portion,and

FIG. 5 is a section view taken along a line V-V in FIG. 4 showing thearrangement of the dynamic vibration absorbing portion being engagedwithin the free end portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Example of Work Vehicle]

With reference to the accompanying drawings, a riding lawnmower as anexample of the work vehicle relating to the present invention will beexplained. FIG. 1 shows a left side view of the riding type lawnmower.FIG. 2 shows a plan view of the riding type lawnmower. Incidentally, inthis detailed description, unless indicated otherwise, a word “front”means the front (forward) side with respect to a vehicle body front/reardirection (traveling direction). A word “rear” means the rear (rearwardor reverse) side with respect to the vehicle body front/rear direction(traveling direction). Further, a language “left/right direction” or“lateral direction” means a vehicle body transverse direction (vehiclebody width direction) perpendicular to the vehicle body front/reardirection. Also, a word “upper” and a word “lower” respectively refer topositional relationship in the perpendicular direction (verticaldirection) of the vehicle body, indicating relationship in terms ofground clearance height.

This riding lawnmower includes a vehicle body frame 10 as a vehiclebody, a pair of left and right front wheels 1 a, 1 b, a pair of left andright driving wheels 2 a, 2 b, a battery 7, a driver's seat 11, and aROPS frame 12. The pair of left and right driving wheels 2 a, 2 b andthe pair of left and right front wheels 1 a, 1 b movably support thevehicle body, and the pair of left and right front wheels 1 a, 1 b arefreely rotatable caster wheels. The pair of left and right drivingwheels 2 a, 2 b are rotatably and independently driven by electricmotors 5 a, 5 b respectively as a pair of left and right “motors” (primemovers). Though not shown, the vehicle body frame 10 is supported by thepair of left and right front wheels 1 a, 1 b and the pair of left andright driving wheels 2 a, 2 b via a suspension.

The battery 7 is disposed at a rear portion of the vehicle body frame 10and the driver's seat 11 is disposed on more front side than the battery7. The ROPS frame 12 is mounted erect on the vehicle body frame 10upwardly from between the driver's seat 11 and the battery 7. Beneaththe vehicle body frame 10 and at the space formed between the frontwheels 1 a, 1 b and the driving wheels 2 a, 2 b, a mower unit 3 ismounted. This mower unit 3 is suspended from the vehicle body frame 10to be lifted up/down via a lift link mechanism 13. The mower unit 3 is aside-discharge type and this mower unit 3 is provided with two rotarymowing blades 8, 8. Each one of the mowing blades 8, 8 is configured tobe rotatably driven by a mower motor (not shown).

A floor plate 14 is formed on more front side than the driver's seat 11and this floor plate 14 serves a “footrest” for a riding person(driver). From a front portion of the floor plate 14, a brake pedal 16protrudes rearwardly upwards. On the left and right opposed sides of thedriver's seat 11, there are disposed a pair of left and rightmaneuvering levers 15 a, 15 b. Each one of the pair of maneuveringlevers 15 a, 15 b is supported to the vehicle body frame 10 to bepivotable about a horizontal axis in the vehicle body transversedirection and configured to be capable of adjusting a rotational speedof corresponding one of the pair of left and right electric motors 5 a,5 b.

The riding person can adjust the rotational speed of the respectiveelectric motor 5 a, 5 b by pivotally operating the respective left andright maneuvering levers 15 a, 15 b. Based on a pivoted angle of theleft maneuvering lever 15 a, an ECU will calculate a rotational speed ofthe left driving wheel 2 a, namely, the rotational speed of the leftelectric motor 5 a. Similarly, based on a pivoted angle of the rightmaneuvering lever 15 b, the ECU will calculate a rotational speed of theright driving wheel 2 b, namely, the rotational speed of the rightelectric motor 5 b. When different power values are fed to the left andright electric motors 5 a, 5 b, the left driving wheel 2 a and the rightdriving wheel 2 b can be driven to rotate at different rotational speedsfrom each other. And, based on this speed difference between the leftand right driving wheels 2 a, 2 b, a turning of the riding lawnmower iseffected.

[Dynamic Vibration Absorbing Portion]

As shown in FIG. 2 and FIG. 3, at the free end portions of the left andright maneuvering levers 15 a, 15 b respectively, a pair of dynamicvibration absorbing portions 30 a, 30 b are supported. The respectivepair of left and right maneuvering levers 15 a, 15 b protrude upwardsfrom their pivotal base end portions and upper end portions of themaneuvering levers 15 a, 15 b are bent inwards in the vehicle bodytransverse direction. Namely, the free end portions of the respectiveleft and right maneuvering levers 15 a, 15 b extend along the vehiclebody transverse direction. And, at these free end portions extendingalong the vehicle body transverse direction, grips 21, 21 are provided.Each grip 21, 21 is used for the riding person (driver) to effect anoperation of adjusting the rotational speed of the respective electricmotors 5 a, 5 b. The grip 21 is a sponge member formed of e.g. ethylenepropylene rubber or the like, with the sponge member being wound aroundthe free end portion.

In operation, the riding person will grip the pair of left and rightgrips 21, 21 respectively and can pivot the left maneuvering lever 15 aand the right maneuvering lever 15 b respectively along the vehicle bodyfront-rear direction. The left dynamic vibration absorbing portion 30 ais supported at more free end side of the left maneuvering lever 15 athan the grip 21. The right dynamic vibration absorbing portion 30 b issupported at more free end side of the right maneuvering lever 15 b thanthe grip 21. The dynamic vibration absorbing portions 30 a, 30 brespectively extends to the vehicle body transverse inner side on morefree end side than the grip 21.

Each the dynamic vibration absorbing portion 30 a, 30 b respectivelyincludes a rubber body 31 as “an elastic body” and a weight 32. Theweight 32 is provided in the form of a solid cylindrical body and therubber body 31 too is provided in the form of a cylindrical body. Theweight 32 is made of a metal, but can be made of plastic, wood, rubber,etc. or can be made of a composite of these materials also. One endportion of the rubber body 31 in its longitudinal direction is formedlike a solid cylinder and this one end portion is supported to the freeend portion of the respective left and right maneuvering levers 15 a, 15b. Namely, at the free end portion of the left maneuvering lever 15 a,the one end portion of the solid cylinder of the rubber body 31 of thedynamic vibration absorbing portion 30 a is supported. And, at the freeend portion of the right maneuvering lever 15 b, the one end portion ofthe solid cylinder of the rubber body 31 of the dynamic vibrationabsorbing portion 30 b is supported. The longitudinal center portion ofthe rubber body 31 is formed as a hollow cylinder and the insidediameter of this hollow portion is equal to or slightly smaller than theoutside diameter of the weight 32. The weight 32 is engaged within thelongitudinal center portion of the rubber body 31, namely, its hollowportion.

FIG. 3 shows relationship between the maneuvering levers 15 a, 15 b andthe dynamic vibration absorbing portions 30 a, 30 b in the form of avibration model with two degrees of freedom. In the instant embodiment,the left and right maneuvering levers 15 a, 15 b respectively constitutethe master vibration system, whereas the grip 21 corresponds to a weightbody M1 of the master system. Of the respective left and rightmaneuvering levers 15 a, 15 b, its more base end side than the grip 21corresponds to the master system spring k1 of the vibration model.Further, the respective dynamic vibration absorbing portions 30 a, 30 bconstitutes the slave vibration system of the vibration model. Therubber body 31 corresponds to a spring k2 and a damper (c) in the slavevibration system and the weight 32 corresponds to the weight body M2 inthe slave vibration system.

The weight of the weight 32, the spring constant of the spring k2 of therubber body 31 and a damping coefficient of the damper (c) of the rubberbody 31 together determine the natural frequency of the respectivedynamic vibration absorbing portions 30 a, 30 b. For this reason, theweight of the weight 32, the spring constant and the damping coefficientof the rubber body 31 will be adjusted such that the natural frequencyof the respective dynamic vibration absorbing portions 30 a, 30 b mayagree with the resonance frequency of the respective left and rightmaneuvering levers 15 a, 15 b. With this arrangement, in the resonancefrequency of the respective left and right maneuvering levers 15 a, 15b, the respective dynamic vibration absorbing portions 30 a, 30 b willresonate in the reverse phase relative to the vibration of themaneuvering levers 15 a, 15 b. With this, the vibration of the grip 21of the respective maneuvering levers 15 a, 15 b may be cancelled outeach other, thus suppressing vibration of the grip 21, 21. In this way,the respective pair of the dynamic vibration absorbing portions 30 a, 30b are configured to be supported to the free end portion of therespective maneuvering levers 15 a, 15 b and are capable of suppressingvibration of the respective maneuvering levers 15 a, 15 b. The springconstant and the damping coefficient of the rubber body 31 will beappropriately adjusted via choice of material and/or shape of the rubberbody 31.

Further, as shown in FIG. 4 and FIG. 5, in case the free end portion ofthe respective maneuvering levers 15 a, 15 b is formed like a hollowpipe, the dynamic vibration absorbing portion 30 a can be engaged withinthe maneuvering lever 15 a and the dynamic vibration absorbing portion30 b can be engaged within the maneuvering lever 15 b. FIG. 5 shows asection at the portion denoted by the line V-V in FIG. 4. The rubberbody 31 is engaged within the maneuvering lever 15 a. The rubber body 31is also engaged within the maneuvering lever 15 b. Like the arrangementdescribed above with reference to FIG. 3, the rubber body 31 is formedlike a hollow cylinder and the weight 32 is engaged within the hollowportion of the rubber body 31. The inside diameter of the hollow portionof the rubber body 31 is equal to or slightly smaller than the outsidediameter of the weight 32.

To the arrangements of the rubber body 31 and the weight 32 shown inFIG. 4 and FIG. 5 also, the vibration model with two degrees of freedomshown in FIG. 3 is applicable. The respective left and right maneuveringlevers 15 a, 15 b constitutes the master vibration system; and themaneuvering lever 15 a, 15 b and the grip 21 correspond to the mastersystem weight body M1 in the vibration model. Of the respective left andright maneuvering levers 15 a, 15 b, the more base end side than thegrip 21 corresponds to the master system spring k1 in the vibrationmodel. The rubber body 31 corresponds to a spring k2 and a damper (c) inthe slave vibration system. The weight 32 corresponds to the weight bodyM2 in the slave vibration system. In the respective dynamic vibrationabsorbing portions 30 a, 30 b shown in FIG. 4 too, the weight of theweights 32, 32, the spring constant and the damping coefficient of therubber bodies 31, 31 will be adjusted such that the natural frequency ofthe respective dynamic vibration absorbing portions 30 a, 30 b may agreewith the resonance frequency of the respective left and rightmaneuvering levers 15 a, 15 b.

Further Embodiments

(1) In the foregoing embodiment, the electric motors 5 a, 5 b were shownas the motors (prime movers). These electric motors 5 a, 5 b can bereplaced by engines respectively. Further alternatively, the pair ofleft and right motors can be combination of a single engine and a pairof left and right torque converters. Namely, it is possible to arrangesuch that a pair of left and right torque converters can distributepower from the signal engine independently to the pair of left and rightdriving wheels 2 a, 2 b and that torque transmission degrees by the pairof left and right torque converters are adjustable by the respectivemaneuvering levers 15 a, 15 b.

(2) In the foregoing embodiment, the pair of dynamic vibration absorbingportions 30 a, 30 b are supported on more free end side than therespective grips 21, 21. However, the arrangement is not limitedthereto. For instance, the pair of dynamic vibration absorbing portions30 a, 30 b can be supported to the respective free ends of the grips 21,21 in the respective left and right maneuvering levers 15 a, 15 b or canbe supported at the longitudinal center portions of the respective grips21, 21.

(3) The dynamic vibration absorbing portions 30 a, 30 b respectivelyextend to the inner side of the vehicle body on more free end side thanthe grips 21, 21. The invention is not limited to this embodiment. Forinstance, the dynamic vibration absorbing portions 30 a, 30 brespectively can extend to the upper side of the vehicle body from thefree end portions or can extend to the lower side of the vehicle bodyfrom the free end portions. Further alternatively, the dynamic vibrationabsorbing portions 30 a, 30 b respectively can extend progressively withan inclination to the lateral outer side of the vehicle body as theyextend away from the free end portions.

(4) In the foregoing embodiment, the pair of the dynamic vibrationabsorbing portions 30 a, 30 b respectively is provided with the rubberbody 31 and the weight 32. The invention is not limited to thisembodiment. For instance, the rubber body 31 can be replaced by a coilspring, a plate spring or the like formed of metal or plastic. Further,the rubber body 31 and the weight 32 can be provided as an integralbody.

(5) In the foregoing embodiment, the weight 32 is engaged within thehollow portion of the rubber body 31. The invention is not limited tothis embodiment. For instance, one left/right end portion of the rubberbody 31 can be connected to the grip 21 and the other left/right end ofthe rubber body 31 can be connected to the weight 32.

(6) The work vehicle of this invention is not limited to the riding typelawnmower. The inventive work vehicle can be a fertilizer spreadervehicle or an insecticide or drug spreader vehicle or can even be afield transporter vehicle or a snow plow vehicle.

1. A work vehicle comprising: a vehicle body; a pair of left and rightdriving wheels that movably support the vehicle body; a pair of motorscapable of rotatably driving the left and right driving wheelsrespectively; a pair of maneuvering levers pivotally supported to thevehicle body to be pivotable about a horizontal axis extending in avehicle body transverse direction and capable of adjusting rotationalspeeds of the left and right driving wheels respectively; and a pair ofdynamic vibration absorbing portions supported to respective free endportions of the maneuvering levers and capable of suppressing vibrationsof the maneuvering levers.
 2. The work vehicle of claim 1, wherein: atthe free end portion, there is provided a grip for a person riding thework vehicle to effect an operation of adjusting a rotational speed ofthe motor; and the dynamic vibration absorbing portion is supported onmore free end side than the grip.
 3. The work vehicle of claim 1,wherein: the dynamic vibration absorbing portion includes an elasticbody and a weight; and of the dynamic vibration absorbing portion, theelastic body is supported to the free end portion.
 4. The work vehicleof claim 3, wherein: the elastic body, at its center portion in thelongitudinal direction, is formed like a hollow cylinder; and the weightis engaged within the hollow center portion of the elastic body.
 5. Thework vehicle of claim 1, wherein: the free end portion is formed like ahollow pipe; and the dynamic vibration absorbing portion is engagedwithin the hollow portion of the free end portion.
 6. The work vehicleof claim 5, wherein: the dynamic vibration absorbing portion includes anelastic body and a weight; the elastic body is formed like a hollowcylinder; and the weight is engaged within a hollow center portion ofthe elastic body.